1. Field of the Invention
The present invention relates generally to testing of electrical devices such as semiconductor devices and printed circuit boards (PCBs). More particularly, the present invention relates to a carrier for holding resilient contact probes, various resilient contact probes, and related assemblies that may be used to perform wafer-level burn-in and testing of components on semiconductor wafers or other electrical devices.
2. State of the Art
It is advantageous in semiconductor processing to detect and screen out defective integrated circuits (ICs) as early as possible in the fabrication process. Many completed ICs fail within the first few months or weeks of use due to processing defects. Such a defect profile is commonly known as “infant mortality” and is clearly very undesirable and unacceptable for a customer purchasing an IC for use with other components in higher level packaging. To discover those circuits that are susceptible to infant mortality, IC fabrication processes conventionally include high temperature and cyclical temperature testing of ICs for extended periods of time before shipping products to a customer.
In a typical semiconductor fabrication process, a multiplicity of identical integrated circuits is formed as individual semiconductor dice on a semiconductor wafer or other bulk semiconductor substrate. Such a multiplicity of integrated circuits may number in the hundreds, or even thousands (such as in a 300 mm wafer) of individual semiconductor dice which are generally repeated across the wafer in a two-dimensional array. Once the integrated circuits are fabricated at semiconductor die locations on a semiconductor wafer, the semiconductor dice are then tested to determine which dice are at least nominally functional with such a determination performed, generally, by probe testing each die individually. The probing of individual semiconductor dice may be performed using probe equipment while the dice are still in wafer form. Currently, expensive probe equipment contacts each bond pad on an individual die with a separate probe. A typical probe test requires that each die be probed in order to determine the correct and acceptable functionality of each die.
Upon the identification of functional and nonfunctional semiconductor dice, the dice are then separated or singulated from the semiconductor wafer by way of a conventional dicing process, such as by using a wafer saw. Following singulation, functional dice may be packaged into separate integrated circuit packages or may undergo further processing prior to assembly with other dice and components in a higher-level assembly, which itself may be packaged. Once the semiconductor dice have been packaged or prepared for packaging within a higher level assembly, more thorough electrical testing is performed to determine whether each packaged integrated circuit properly performs the functionality for which it was designed. Upon successful package testing, integrated circuits may be sold or integrated into higher assemblies.
One system for testing individual dice is disclosed in U.S. Pat. No. 5,791,914 to Loranger et al. (hereinafter “the '914 Loranger Patent”). The '914 Loranger Patent discloses a socket-based electrical contactor. The socket based electrical contactor employs a two piece system for captivating a plurality of compression springs. A guide plate and a socket body captivates the plurality of compression springs that provide an electrical connection between a PCB and a semiconductor die to be tested.
While the socket-based electrical contactor of the '914 Loranger Patent enables the electrical testing of a semiconductor die, it suffers from several problems. For instance, the compression springs used to provide the electrical connection between the semiconductor die and the PCB exhibit very little lateral stability, resulting in inaccuracy when attempting to contact the terminal pads of the PCB and the bond pads of the semiconductor die. Furthermore, the same load is applied to the terminal pads of the PCB and the bond pads of the semiconductor die, which may result in a poor electrical connection therebetween. This is because the PCB, typically an interface test board, often has contaminated terminal pads with films and other contaminants thereon preventing a reliable electrical connection. Also, a two piece system is used to captivate the compression springs, adding additional parts and increasing cost and assembly time to the electrical contactor. Additionally, the socket based contactor is designed to test only individual semiconductor dice.
Multi-piece plate fixtures have been developed that hold spring contacts for testing circuit boards. For instance, U.S. Pat. No. 6,127,835 to Kocher et al. discloses such a fixture. U.S. Pat. No. 6,127,835 to Kocher et al. also purports to disclose employing a retainer sheet made of a rubber material such as latex, or a fine-mesh nylon material, which functions to hold the test probes in place in the assembled fixture.
Accordingly, there is a need for a system to test electrical devices such as integrated circuits and PCBs that employs resilient contact probes that have improved lateral stability and accuracy. Additionally, there is a need to enable mechanical loading of the terminal pads of the printed circuit board of the test apparatus and the electrical contacts of the electrical device tested to different levels or degrees to provide a reliable electrical connection therebetween. Furthermore, there is a need for a system to captivate resilient contact probes that is less costly and has fewer parts, making fabrication thereof less problematic. It is also desirable to be able to test an entire wafer in the test system as opposed to only individual semiconductor dice.